1. Technical Field
The present invention relates to a liquid level detecting device which detects the liquid level of liquid in a tank.
2. Background Art
Traditionally, a liquid level detecting device is known which detects the liquid level of liquid in a tank with an electrostatic capacity method of detecting the liquid level from a difference between the electrostatic capacity of gas and that of the liquid (refer to JP-A-563-079016 and Japanese Patent No. 2705257).
In the JP-A-563-079016, it is disclosed that the dielectric constant of the liquid is calculated from the capacity between the electrodes of a reference electrode which is always immersed in the liquid, and the liquid level is detected from the capacity between the electrodes of a tine electrode using the dielectric constant.
In Japanese Patent No. 2705257, it is disclosed that the dielectric constant is corrected using electrodes of different lengths, and a warning lamp is turned on if the liquid level becomes below a specified level.
However, there are the following problems in the traditional liquid level detecting device. FIG. 6 is a figure which shows a liquid leak state in a traditional liquid level detecting device. There is a problem that, as shown in FIG. 6, when there is a liquid leak between electrodes 111 and 112 or there is a drop of dew in the vapour phase part due to a vapor (steam) state or dew condensation in the tank, a liquid level detecting device 100 detects mistakenly when the liquid surface is located above the real liquid level, and does not make a warning lamp turned on.
There is the same problem that the liquid surface cannot be detected precisely when liquids of different dielectric constants are separated in the tank.
The present invention is made in view of the above circumstances, and the object of the present invention is to provide a liquid level detecting device which can detect liquid level precisely even when there is a liquid leak or a drop of dew in the vapor phase part or when liquids of different dielectric constants are separated.